1. Field of the Invention
The present invention relates to phosphinines and metal complexes thereof, the preparation of the phosphinines and their use as ligands in catalytic reactions.
2. Discussion of the Background
The reaction of olefinic compounds, carbon monoxide and hydrogen in the presence of a catalyst to form aldehydes having one more carbon atoms is known as hydroformylation (oxo process). As catalysts in these reactions, use is frequently made of compounds of transition metals of group VIII of the Periodic Table of the Elements, in particular rhodium and cobalt compounds. Hydroformylation using rhodium compounds generally offers the advantage of higher selectivity compared to the cobalt-catalyzed reaction and is thus usually more economical. The rhodium-catalyzed hydroformylation is usually carried out using complexes comprising rhodium and preferably trivalent phosphorus compounds as ligands. Known ligands are, for example, compounds from the classes of phosphines, phosphites and phosphonites. A good review of the hydroformylation of olefins may be found in B. Cornils, W. A. Herrmann, “Applied Homogeneous Catalysis with Organometallic Compounds”, Vol. 1&2, VCH, Weinheim, N.Y., 1996.
Each catalyst system (cobalt or rhodium) has its specific advantages. Different catalyst systems are therefore used depending on the starting material and target product, as the following examples show. If rhodium and triphenylphosphine are employed, α-olefins can be hydroformylated at relatively low pressures. An excess of triphenylphosphine is generally used as phosphorus-containing ligand, with a high ligand/rhodium ratio being necessary to increase the selectivity of the reaction in favor of the commercially desired n-aldehyde product.